1. Field of the Invention
The present invention relates to an imaging apparatus and an imaging system which are configured to be supplied with electric power through a signal communication unit, such as a signal cable using PoE (Power over Ethernet).
2. Description of the Related Art
Conventional monitoring cameras include cameras called CCTV (Closed-Circuit TV). The CCTV camera outputs a video signal of NTSC format, for example, over a video cable. The video signal is recorded by a time-lapse recorder and is displayed on a monitor for surveillance. In addition, cameras configured to be supplied with electric power through a video cable, so-called one-cable power supply system cameras, have been put into practical use.
In recent years, the use of monitoring cameras via networks has become prevalent. Surveillance with monitoring cameras via networks facilitates linking up with a security system, such as an entrance access security system, for example. Therefore, monitoring systems have become far more convenient today than ever before.
In the field of networks, a system has been developed which can supply electric power to cameras using PoE via a LAN cable. As a result, cameras can be driven without the need for an external power supply located near the camera. In particular, monitoring cameras sometimes need to be installed outdoors even if there is no external power supply. The one-cable power-supply system not only simplifies wiring, for example, but also obviates installation cost of an external power supply. Therefore, the one-cable power supply system can meet the market demand.
Meanwhile, recent monitoring cameras are equipped with diverse functions. Some monitoring cameras are equipped with AF (Auto Focus), power zoom, and pan and tilt driving functions.
The upper limit in the standards for power consumption of external devices in PoE is 12.95 W. From a practical point of view, however, the upper limit is 10 W or so. Power consumption in cameras includes, as typical examples, 2.5 W for video output, 2 W for video and signal transmission, 0.7 W for focusing, 0.8 W for zoom, 3 W for pan, 3 W for tilt, and 0.7 W for IR (infrared) cut filter switching. If all of those functions are driven at the same time, a total of about 13 W is required. Incidentally, so far, there have been no cameras using PoE and equipped with pan and tilt functions, and, therefore, such a problem as mentioned above has not been recognized.
In a camera discussed in Japanese Patent Application Laid-Open No. 2002-131806, electric power is supplied through a USB (Universal Serial Bus) cable to enable pan and tilt functions. However, that camera is not equipped with AF or zoom functions. Moreover, an image is distorted and picture quality is sacrificed as a result of reducing power consumption as much as possible.
In Japanese Patent Application Laid-Open No. 08-279952, a description is made of pan and tilt driving functions. However, only a camera platform unit is disclosed, and no mention is made of video output and so on.
A multifunction camera includes motors to drive various functions and, therefore, requires a large amount of electric power. However, as for monitoring cameras, power supply systems differ with installation environments. For example, in some cases, a simplified power supply system using PoE can be installed. In other cases, a dedicated AC adapter can be used. In the former situation, the power supply capacity is relatively small. In the latter, the power supply capacity is more than what is required, so that the operating performance of a camera can be utilized to the maximum. As has been described, since power supply environments are of great variety, there has been no camera that can meet diverse environments flexibly.